Washing machine and control method thereof

ABSTRACT

A washing machine capable of performing washing by increasing a water level when an overload of a motor is detected, and a control method thereof. The washing is performed by detecting an overload of the motor using a load detecting circuit and changing a water level to a highest water level when the overload is detected. Thus, a burning smell may not be caused from the motor by preventing stalling of the motor, and washing performance may be maintained since the motor is continuously operated without stopping.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Patent Application No. 10-2013-0134435, filed on Nov. 6, 2013 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND

1. Field

Embodiments of the present disclosure relate to a washing machine that performs washing by increasing a water level when an overload of a motor is detected, and a control method thereof.

2. Description of the Related Art

A washing machine (e.g., an electric washing machine) generally includes a tub to retain water (wash water or rinse water), a washing tub rotatably installed in the tub to accommodate laundry, a pulsator rotatably installed in the washing tub to generate a water stream, and a motor to generate driving force to rotate the washing tub and the pulsator. The washing machine removes contaminants from laundry using the water stream and the surfactant action of a detergent.

The washing machine performs washing through a series operations including a washing cycle to remove contaminants from the laundry using water containing a dissolved detergent (specifically, wash water), a rinsing cycle to remove lather and residual detergent from the laundry using water which does not contain the detergent (specifically rinse water), and a spin-drying cycle to remove water from the laundry by rotating the laundry at high speed. When washing is performed through the series of operations, the washing cycle, the rinsing cycle, and the spin-drying cycle respectively drive the motor at respective target motor RPMs and target operation factors. The motor RPM and the operation factor are set according to weight (load) of laundry in each cycle, and the motor is rotated at a speed as instructed according to the set RPM and operation factor.

However, the motor is stalled by a heavy weight (load) of laundry, and thus it is difficult to achieve a desired speed as instructed.

Besides, rotation force of the motor varies according to the water level and increases as the water level increases. Thus, when a heavy weight of laundry is washed at a low water level, the motor is excessively driven due to a control operation by which available current or voltage limit of the motor is used to raise the motor RPM to a target RPM. Therefore, the motor is overloaded so that temperature of the motor increase to cause burning smell thereof. As a result, operation of the motor may be ceased, thereby deteriorating washing performance.

SUMMARY

Therefore, it is an aspect of the present disclosure to provide a washing machine capable of performing washing by increasing a water level when an overload of a motor is detected and a control method thereof.

Additional aspects of the disclosure will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the disclosure.

In accordance with one aspect of the present disclosure, a method of controlling a washing machine including a washing tub to accommodate laundry, a pulsator rotatably installed in the washing tub, and a motor to rotate the pulsator include setting a level of water supplied to the washing tub, rotating the motor clockwise and counterclockwise after supplying water to the washing tub up to the set water level, detecting an overload of the motor while rotating the motor clockwise and counterclockwise, and changing the set water level to a higher water level when the overload of the motor is detected and performing cycles of the washing machine.

The setting of the water level may be performed after detecting weight of the laundry.

The setting of the water level may be performed by setting the water level according to the detected weight of the laundry.

The setting of the water level may be performed by selecting the water level according to manipulation by a user.

The detecting of the overload of the motor may be performed after a water supplying cycle of initially supplying water to wash the laundry.

The detecting of the overload of the motor may be performed before performing the cycles of the washing machine.

The rotating of the motor clockwise and counterclockwise may include rotating the motor in one direction for a first time period, stopping the rotation of the motor for a second time period after rotating the motor in the one direction, rotating the motor in the opposite direction for a third time period after the second time period, and stopping the rotation of the motor for a fourth time period after rotating the motor in the opposite direction.

The method may further include counting pulse signals generated by counter electromotive force of the motor while the motor is stopped.

The method may further include counting a time period taken to rotate the motor clockwise and counterclockwise, and stopping the rotation of the motor clockwise and counterclockwise when the counted time period is greater than a predetermined time period.

The detecting of the overload of the motor may be performed by determining that the motor is overloaded when a sum of the counted pulse signals is less than a reference value.

The changing of the set water level may be performed by changing the set water level to a highest water level.

The rotating of the motor in one direction may be performed by rotating the motor in a regular direction for the first time period while maintaining a constant motor RPM.

The rotating of the motor in the opposite direction may be performed by rotating the motor in the reverse direction for the third time period while maintaining a constant motor RPM.

The method may further include changing the motor RPM when the motor is rotated clockwise and counterclockwise.

The method may further include motor driving time or motor stopping time while rotating the motor clockwise and counterclockwise.

In accordance with another aspect of the present disclosure, a method of controlling a washing machine including a washing tub to accommodate laundry, a pulsator rotatably installed in the washing tub, and a motor to rotate the pulsator and the washing tub includes rotating the motor clockwise and counterclockwise after a water supplying cycle to supply water to a set water level for washing the laundry, detecting an overload of the motor while rotating the motor clockwise and counterclockwise, and changing the set water level to a highest water level when the overload of the motor is detected and performing cycles of the washing machine.

In accordance with another aspect of the present disclosure, a washing machine includes a washing tub to accommodate laundry, a pulsator rotatably installed in the washing tub, a motor to rotate the pulsator, a load detector to detect a weight of the laundry, and a controller to perform an overload detecting cycle by rotating the motor clockwise and counterclockwise after supplying water to the washing tub up to a set water level, and detecting an overload of the motor using the load detector while the motor is rotated clockwise and counterclockwise. The overload detecting cycle to detect an overload by performing an operation of rotating the motor clockwise and counterclockwise for a predetermined time period may include rotating the motor in one direction for a first time period after supplying water to the washing tub, stopping the rotation of the motor for a second time period after rotating the motor in the one direction, rotating the motor in the opposite direction for a third time period after the second time period, and stopping the rotation of the motor for a fourth time period after rotating the motor in the opposite direction.

The controller may count pulse signals generated by counter electromotive force of the motor while the motor is stopped during the rotation of the motor, compares a sum of the counted pulse signals with a reference value, and determines that the motor is overloaded when the counted pulse is less than the reference value.

The controller may set the water level according to the detected weight of the laundry.

The controller may change the set water level to a higher water level when the overload of the motor is detected.

The washing machine may further include an input unit to select a level of water supplied to the washing tub, wherein the controller changes the selected water level to a higher water level when an overload of the motor is detected.

The controller may change the set water level to a highest water level.

According to the washing machine and the control method thereof, the washing is performed by detecting an overload of the motor using a load detecting circuit and changing a water level to a highest water level when the overload is detected. Thus, a burning smell may not be caused from the motor by preventing stalling of the motor, and washing performance may be maintained since the motor is continuously operated without stopping.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects of the disclosure will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a cross-sectional view illustrating a configuration of a washing machine according to an embodiment of the present disclosure;

FIG. 2 is a control configuration of a washing machine according to an embodiment of the present disclosure;

FIG. 3 is a circuit diagram of a load detector according to an embodiment of the present disclosure;

FIG. 4 is a table illustrating pulse counts with respect to water levels obtained using a load detector according to an embodiment of the present disclosure;

FIG. 5 is a flowchart illustrating a method of controlling a washing machine according to an embodiment of the present disclosure;

FIG. 6 is a diagram illustrating water levels of a washing machine according to an embodiment of the present disclosure;

FIG. 7 is a flowchart illustrating a rotation operation of a motor during an overload detecting cycle of a washing machine according to an embodiment of the present disclosure;

FIG. 8 is a graph illustrating motor driving profile 1 during an overload detecting cycle of a washing machine according to an embodiment of the present disclosure;

FIG. 9 is a graph illustrating motor driving profile 2 during an overload detecting cycle of a washing machine according to an embodiment of the present disclosure; and

FIG. 10 is a graph illustrating motor driving profile 3 during an overload detecting cycle of a washing machine according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

Reference will now be made in detail to the embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout.

FIG. 1 is a cross-sectional view illustrating a configuration of a washing machine 1 according to an embodiment of the present disclosure.

Referring to FIG. 1, the washing machine 1 according to the illustrated embodiment includes a cabinet 10 having an approximate box-shape and defining an external appearance of the washing machine 1, a tub 11 installed in the cabinet 10 to retain water (wash water or rinse water), a washing tub 12 rotatably mounted in the tub 11 to accommodate laundry, and a pulsator 13 rotatably installed in the washing tub 12 to generate a water stream while rotating clockwise or counterclockwise (in a regular direction or in the reverse direction), and has a vertical shaft.

The washing tub 12 is formed in a cylindrical shape having an open top and has a plurality of drainage holes 12 a on the lateral surface thereof. A balancer 12 b may be mounted at an upper portion of the washing tub 12 to ensure stable rotation of the washing tub 12 at high speed.

Installed at an outer lower portion of the tub 11 are a washing motor 14 to generate driving force to rotate the washing tub 12 and the pulsator 13 and a power switching device 15 to simultaneously or selectively transfer the driving force generated by the washing motor 14 to the washing tub 12 and the pulsator 13.

A spin-drying shaft 16 having a hollow inside is couple to the washing tub 12. A washing shaft 17 installed in a hollow portion of the spin-drying shaft 16 may be coupled to the pulsator 13 through a washing shaft coupling portion 18.

The washing motor 14 is a direct drive (DD) motor having a variable speed function. The washing motor 14 may simultaneously or selectively transfer driving force to the washing tub 12 and the pulsator 13 depending on an ascending or descending movement of the power switching device 15.

Alternatively, a universal motor including a field coil and an armature or a brushless direct current (BLDC) motor including a stator and a rotor may be used as the washing motor 14, and any other motors applicable to the washing machine 1 may also be used. In addition, the washing motor 14 may be configured as a belt-type.

The power switching device 15 may include an actuator 15 a to generate driving force for power switching, a rod 15 b to rectilinearly move in accordance with the movement of the actuator 15 a, and a clutch 15 c connected to the rod 15 b to turn in accordance with the movement of the rod 15 b.

The washing motor 14 may rotate only the washing shaft 17 in the regular direction or the reverse direction while the washing shaft 17 and the spin-drying shaft 16 are disengaged from each other, such that the pulsator 13 is rotated clockwise or counterclockwise to soak laundry, dissolve a detergent, perform a washing cycle, perform a soak rinsing cycle, and loosen the laundry.

In addition, the washing motor 14 may rotate the washing shaft 17 and the spin-drying shaft 16 in the regular direction or the reverse direction while the washing shaft 17 and the spin-drying shaft 16 are engaged to each other, such that the pulsator 13 and the washing tub 12 are simultaneously rotated in on direction to perform a shower rinsing cycle and a spin-drying cycle.

In addition, a water level sensor 19 that senses a frequency varying according to a water level is installed at a lower inner portion of the tub 11 to sense the amount (level) of water in the tub 11.

A drain 20 is formed at the bottom of the tub 11 to discharge water in the tub 11 to the outside, and a first drainpipe 21 is connected to the drain 20. A drainage motor 22 to regulate drainage is installed at the first drainpipe 21, and a second drainpipe 23 is connected to an outlet of the drainage motor 22 to discharge the water to the outside.

A door 25 that is opened or closed is installed at an upper side of the cabinet 10 to put laundry into the washing tub 12 or take the laundry out of the washing tub 12. A top-cover 26 to which the door 25 is seated is installed at the upper side of the cabinet 10.

The top cover 26 has an inlet 27 through which laundry is put into the washing tub 12 or taken out of the washing tub 12, and the inlet 27 is opened or closed by the door 25.

A water supply pipe 40 to supply water to the tub 11 is installed at an upper portion of the cabinet 10. One end of the water supply pipe 40 is connected to an external water source, and the other end of the water supply pipe 40 is connected to a detergent feed unit 41. Water supplied through the water supply pipe 40 is introduced into the tub 11 together with a detergent via the detergent feed unit 41. A water supply valve 42 is installed at the water supply pipe 40 to control supply of water.

Meanwhile, the tub 11 may be supported against the cabinet 10 by a suspension device 43. A check switch 44 may be installed between the tub 11 and the cabinet 10 to detect shaking of the washing tub 12 which may occur when the user touches the washing tub 12 to take out the laundry. In addition, the check switch 44 may detect excessive vibration of the tub 11 which occurs before the cabinet 10 collides with the tub 11 according to eccentric rotation of the washing tub 12 caused by unbalanced distribution of the laundry.

FIG. 2 is a control configuration of a washing machine 1 according to an embodiment of the present disclosure.

Referring to FIG. 2, the washing machine 1 according to the illustrated embodiment includes an input unit 50, a controller 52, a memory 54, a drive unit 56, a display unit 58, and a load detector 60.

The input unit 50, which is manipulated by a user to input instructions to perform washing, rinsing, and spin-drying cycles of the washing machine 1, may include a key, a button, a switch, a touchpad, and any other elements that generate predetermined input data by manipulations such as pushing, touching, pressing, and rotating.

In addition, the input unit 50 may include a plurality of buttons (for power, operation schedule, temperature of wash water, steeping, washing, rinsing, spin-drying, water level selection, and the like) through which instructions related to operation of the washing machine 1 are input by the user. The plurality of buttons may include a water level selection button 51 to select the level of water supplied to the washing machine 1.

When the user selects a desired water level via the water level selection button 51, an LED lamp indicating the selected water level may be turned on to allow the user to confirm the selected water level.

The controller 52 is a microcomputer that controls overall operations of the washing machine 1 such as washing, rinsing, and spin-drying according to operation information input through the input unit 50. In a selected course, the controller 52 sets a target water level (wash water level and rinse water level), a target RPM, a motor operation factor (On/Off time of the washing motor), and duration of washing and rinsing according to weight (load) of laundry.

In addition, the controller 52 may set the target water level (wash water level and rinse water level) as the water level selected by the user through the water level selection button 51.

Thus, the controller 52 performs an overload detecting cycle to detect an overload applied to the washing motor 14 using the load detector after supplying water to a target water level set according to a detected weight (load) of laundry after the laundry is put or a target water level selected through the water level selection button 51 (during the starting process of the washing cycle.

The overload detecting cycle is to determine overload conditions for the washing motor 14 by counting pulses generated while the washing motor 14 is rotated clockwise and counterclockwise at a predetermined RPM (about 500 to 600 RPM) at a predetermined operation factor (about 1.0 sec On/0.7 sec Off) for a predetermined time period (about 30 seconds) under the condition that the laundry is soaked after the laundry is put into the washing tub 12 and water for washing the laundry is supplied thereto.

Thus, the controller 52 controls the washing motor 14 to be protected by detecting overload conditions for the washing motor 14 by measuring the pulses counted by the load detector 60 while the washing motor 14 is rotated clockwise and counterclockwise for a predetermined time period (about 30 seconds), increasing the water level in accordance with the overload conditions of the washing motor 14 (e.g., to the highest water level), and then performing the washing cycle. The overload conditions for the washing motor 14 include heavy weight (load) of the laundry and low water level. Detailed descriptions thereof will be given later with reference to FIGS. 3 and 4.

The memory 54 may store control data to control operation of the washing machine 1, reference data used during the control operation of the washing machine 1, operation data created while the washing machine 1 performs a predetermined operation, setting information such as setting data input through the input unit 50 to make the washing machine 1 perform a predetermined operation, information for use including the number of operation performed by the washing machine 1 and model information of the washing machine 1, and malfunction information including causes or positions of malfunctions in the washing machine 1.

The driving unit 56 drives the washing motor 14, the drainage motor 22, and the water supply valve 42 related to operations of the washing machine 1 according to a driving control signal from the controller 52.

The display unit 58 displays the operating state of the washing machine 1 and the manipulating state of the user according to a display control signal from the controller 52.

The load detector 60 measures the pulses counted during the overload detecting cycle of rotating the washing motor 14 clockwise and counterclockwise for a predetermined time period (about 30 seconds), and inputs the results to the controller 52.

FIG. 3 is a circuit diagram of a load detector 60 according to an embodiment of the present disclosure.

Referring to FIG. 3, the load detector 60 includes a photo coupler 61 turned on/off according to counter electromotive force of the washing motor 14 generated when power supplied to the washing motor 14 for a predetermined time period (e.g., 1.0 seconds) is stopped, a transistor 62 to generate pulse signals via On/Off operations in accordance with the On/Off operations of the photo coupler 61, a pull-up resistor 63 to input high or low pulse signal to the controller 52 in accordance with the On/Off operations of the transistor 62, a condenser 64 to protect the transistor 62 from overcurrent during the On/Off operations of the transistor 62, a condenser 65 to remove noise from the pulse signal input to the controller 52, condensers 66 and 67 connected between the washing motor 14 and the photo coupler 61, and a resistor 68.

When the pulse signals are counted during the overload detecting cycle to detect an overload of the washing motor 14 using the overload detector 60, the pulse count increases as the weight (load) of the laundry decreases, while the pulse count decreases as the weight (load) of the laundry increases due to stalling of the washing motor 14.

In addition, the pulse count increases as the water level increases, while the pulse count decreases as the water level decreases due to a large load applied to the washing motor 14.

FIG. 4 is a table illustrating the pulse signals generated while a washing cycle is performed under a load of towels at each water level and counted using a load detector 60 according to an embodiment of the present disclosure.

As illustrated in FIG. 4, it is confirmed that the pulse count increases as the water level increases, while the pulse count decreases as the water level decreases.

This is because the rotation of the washing motor 14 is facilitated at a higher water level, so that the count of the pulse signals generated by counter electromotive force of the washing motor 14 increases.

On the contrary, the rotation of the washing motor 14 is hindered at a lower water level, so that the count of the pulse signals generated by counter electromotive force of the washing motor 14 decreases.

Hereinafter, a description will be given of procedures and effects of operation of a washing machine and a control method thereof according to an embodiment of the present disclosure.

FIG. 5 is a flowchart illustrating a control method of a washing machine according to an embodiment of the present disclosure. An algorithm for detecting overload conditions for the washing motor 14 by rotating the washing motor 14 clockwise and counterclockwise after supplying water to a target water level is described. FIG. 6 is a diagram illustrating water levels of a washing machine 1 according to an embodiment of the present disclosure.

Referring to FIG. 5, when the user puts laundry into the washing tub 12 and inputs operation information related to operation of the washing machine 1 such as a washing course (e.g., standard course selected by the user among a plurality of washing courses including standard course, wool course, and delicate course) according to the type of the laundry, the operation information selected by the user is input to the controller 52 through the input unit 50.

Accordingly, the controller 52 detects weight (load) of laundry put into the washing tub 12 to conduct the washing cycle (100). The weight of laundry may be detected in various ways. The weight may be detected using the load detector 60. If the load detector 60 is not installed, the weight may be detected, after rotating the washing motor 14 at a weight detection RPM (about 70 to 150 RPM) with a predetermined duty (90 V) applied to the washing motor 14, by using time taken to reach the duty and angular speed. Alternatively, the weight may be detected by using time taken to reach a predetermined speed (or a predetermined RPM) using an instantaneous acceleration of the washing motor 14. Alternatively, as disclosed in Japanese Patent Application Publication Nos. 2002-336593, 2004-267334, and 1995-90077, the weight of the laundry may be detected by applying torque to the washing motor 14 for a predetermined time, directly or indirectly measuring the moment of inertia of the washing tub 12, and then calculating the weight using the second law of motion (i.e., torque=inertial*acceleration).

Alternatively, a commonly known technique of using a load cell may be adopted to detect the weight (load) of the laundry.

When the weight (load) of laundry is detected, the controller 52 sets a motor RPM and operation factor (On/Off time of the motor), a target water level (target wash water level and target rinse water level), and duration of washing and rinsing according to the detected weight (load) of laundry (102).

The setting of the motor RPM and operation factor (On/Off time of the motor), a target wash water level and the target rinse water level, and duration of washing and rinsing according to the detected weight (load) of laundry is performed in the case that a separate instruction related to operation of the washing machine 1 is not additionally input by the user. When the user additionally inputs a separate instruction related to operation of the washing machine 1 (for example, the water level is selected via manipulation of the water level selection button), the motor RPM and operation factor (On/Off time of the motor), the target water level (target wash water level and target rinse water level), and duration of washing and rinsing may be changed according to the user instruction.

Hereinafter, the case in which the user selects a low water level (e.g., a lowest water level of level 1 or 2) via the water level selection button 51 even though a heavy weight (load) of laundry is washed will be described to detect overload conditions for the washing motor 14 according to an embodiment of the present disclosure. Generally, when a target water level (target wash water level and target rinse water level) is automatically set according to the weight (load) of laundry, the water level is selected to be sufficient for the laundry, and thus there is very little probability that the washing motor 14 is overloaded.

This will be described in more detail.

When the user selects a low target water level even though a heavy weight (load) of laundry is washed, the washing motor 14 may be hindered. In this case, the washing motor 14 cannot be rotated at an instructed speed.

Thus, in order to increase the rotation speed of the washing motor 14 to the instructed level, a control operation to increase current or voltage to available current or voltage limit is required. Thus, due to excessive driving of the washing motor 14, the washing motor 14 is overloaded. Accordingly, temperature of the washing motor 14 is increased to cause a smell of burning. As a result, the operation of the washing motor 14 is stopped, and washing performance is deteriorated. Thus, there is a need to detect overload conditions for the washing motor 14.

In FIG. 6, levels of water supplied to the tub 11 are classified into 10 levels (level 1 to level 10). In a 16 Kg washing machine, levels 1 to 3 indicate a lowest water level, levels 4 to 5 indicate a low water level, levels 6 to 7 indicate a medium water level, levels 8 to 9 indicate a high water level, and level 10 indicates a highest water level.

Generally, the washing machine 1 is an apparatus in which laundry is washed using the flow of laundry and water stream respectively generated by rotation of the washing tub 12 or pulsator 13 according to driving of the washing motor 14. When the washing cycle, the rinsing cycle, and the spin-drying cycle are carried out under overload conditions for the washing motor 14, driving current of the washing motor 14 increases. The increase in driving current results in an increase in temperature of the washing motor 14 and a printed board assembly (PBA), thereby influencing durability of the washing motor 14 and increasing power consumption.

Thus, according to the illustrated embodiment, the overload detecting cycle may be performed to optimize the operation of the washing machine 1 (particularly, the washing cycle and the rinsing cycle) without excessively driving the washing motor 14 by detecting overload conditions for the washing motor 14 only using the lowest target water level of level 1 or 2.

Then, the controller 52 drives the water supply valve 42 through the drive unit 56 to supply water (wash water) to a target water level set by the user through the water level selection button 51 (104).

When the water supply valve 42 is operated, the water supply valve 42 is opened and water (wash water) supplied through an external water supply pipe is supplied to the tub 11 along with a detergent via the water supply pipe 40 and the detergent feed unit 41.

Accordingly, the controller 52 determines whether the water level is the same as the target water level (target wash water level) or not by detecting the level of water supplied to the tub 11 using the water level sensor 19, and continues the water supplying operation until the water level reaches the target water level in the tub 11.

When water supplied to the tub 11 reaches the target water level by the water supplying operation, the controller 52 controls the water supply valve 42 to be closed to stop the wash water supplying operation.

When the wash water is supplied up to the target wash water level, the controller 52 rotates the washing motor 14 clockwise and counterclockwise for a predetermined time period (about 30 seconds) to detect overload of the washing motor 14 (106).

The rotating of the washing motor 14 clockwise and counterclockwise for a predetermined time period is to rotate the pulsator 13 clockwise and counterclockwise by coupling the pulsator 13 to the washing shaft 17 of the washing motor 14 and driving the washing motor 14 at a predetermined operation factor (about 1.0 sec On/0.7 sec Off) while maintaining a predetermined RPM (at 500 to 600 RPM, e.g., 530 RPM, capable of strongly rotating the pulsator 13) under the condition that the laundry is soaked after supplying water to the target water level.

When the pulsator 13 is rotated clockwise and counterclockwise by rotating the washing motor 14 clockwise and counterclockwise, rotation force of the washing motor 14 varies according to the weight (load) of laundry accommodated in the washing tub 12 and the water level. That is, as the weight of laundry increases and the water level decreases, the rotation force of the washing motor 14 decreases compared to the instructed speed.

As such, when the washing motor 14 is excessively driven based on rotation force thereof which varies according to the weight (load) of laundry and the water level, the washing motor 14 is overloaded, and the temperature of the washing motor 14 increases.

Thus, the controller 52 counts the pulses to detect overload conditions for the washing motor 14 when the washing motor 14 is stopped (turned off) using the load detector 60 while rotating the washing motor 14 clockwise and counterclockwise for a predetermined time period (about 30 seconds) (108).

Accordingly, the controller 52 determines whether the counted pulse is less than a reference value (a limit of the pulse signal generated at the lowest water level of level 1 or 2) (110).

As a result of determination in operation 110, when the pulse count is less than the reference value, the controller 52 determines that the washing motor 14 is overloaded, changes the water level to the highest water level regardless of the target water level set in operation 102, and performs subsequent operations of the washing machine 1 (particularly, the washing cycle and the rinsing cycle) (112).

The water level is changed to the highest water level under the overload conditions in order not to excessively drive the washing motor 14, and thus the washing motor 14 may be protected.

Meanwhile, as a result of determination in operation 110, when the pulse value is greater than the reference value, the controller 52 determines that the washing motor 14 is not overloaded and performs subsequent operations of the washing machine 1 (particularly, the washing cycle and the rinsing cycle) while maintaining the target water level set in operation 102 (114)

Hereinafter, an algorithm of an overload detecting cycle will be described with reference to FIGS. 7 to 10.

FIG. 7 is a flowchart illustrating rotation operation of a motor during an overload detecting cycle of a washing machine 1 according to an embodiment of the present disclosure. FIG. 8 is a graph illustrating motor driving profile 1 during an overload detecting cycle of a washing machine 1 according to an embodiment of the present disclosure.

First, when the user puts laundry into the washing tub 12 and sets a target water level through the water level selection button 51, water is supplied up to the set target water level.

Then, the controller 52 connects the pulsator 13 with the washing shaft 17 of the washing motor 14 through the power switching device 15 (200). Accordingly, driving force of the washing motor 14 is transferred to the washing shaft 17 through the power switching device 15 to strongly rotate the pulsator 13 clockwise and counterclockwise at a motor RPM of the overload detecting cycle.

Then, the controller 52 initiates the overload detecting cycle of strongly rotating the pulsator 13 clockwise and counterclockwise by driving the washing motor 14 at an operation factor of 1.0 sec motor on/0.7 sec motor off while maintaining a predetermined RPM (about 530 RPM, first RPM) as illustrated in FIG. 7.

To this end, the controller 52 drives the washing motor 14 at the first RPM in the regular direction through the drive unit 56 (202) and counts a time period taken to drive the washing motor 14 at the first RPM in the regular direction so as to determine whether the counted time period is greater than a predetermined first time period (about 1.0 seconds) (204).

As a result of determination in operation 204, when the measured time period is less than the first time period, the controller 52 feeds back to operation 202 and performs subsequent operations.

As such, when the washing motor 14 is rotated at the first RPM for the first time period (1.0 seconds) in the regular direction, the pulsator 13 is strongly rotated in one direction. The strong rotation of the pulsator 13 applies force to laundry accommodated in the washing tub 12, such that laundry items in a close contact with the pulsator 13 are separated from each other to form air bubble layers.

Meanwhile, as a result of determination in operation 204, when the measured time period is greater than the first time period, the controller 52 stops the washing motor 14 through the drive unit 56 (206).

When the washing motor 14 is stopped, counter electromotive force of the washing motor 14 is generated. Due to the generated counter electromotive force, the photo coupler 61 of the load detector 60 performs On/Off operation, and the transistor 62 performs On/Off operation in accordance with the On/Off operation of the photo coupler 61, thereby generating pulse signals.

The high or low pulse signal generated according to the On/Off operation of the transistor 62 is input to the controller 52, and the controller 52 counts the pulse signals (207).

Then, the controller 52 counts a time period taken to stop the washing motor 14 and determines whether the counted time period is greater than a predetermined second time period (about 0.7 seconds) (208).

As a result of determination in operation 208, when the measured time period is less than the second time period, the controller 52 feeds back to operation 206 and performs subsequent operations.

As such, when the washing motor 14 is stopped for the second time period (about 0.7 seconds) after being driven in the regular direction, air bubble layers formed around the pulsator 13 flow between laundry items.

Meanwhile, as a result of determination in operation 208, when the measured time period is greater than the second time period, the controller 52 drives the washing motor 14 at the first RPM in the reverse direction through the drive unit 56 (210) and counts a time period taken to drive the washing motor 14 at the first RPM in the reverse direction, and then determines whether the counted time period is greater than the first time period (212).

As a result of determination in operation 212, when the measured time period is less than the first time period, the controller 52 feeds back to operation 210 and performs subsequent operations.

As such, when the washing motor 14 is rotated at the first RPM for the first time period (1.0 seconds) in the reverse direction, the pulsator 13 is strongly rotated in the reverse direction. In this case, force caused by reaction force of the pulsator 13 strongly rotating in the reverse direction is applied to the laundry while the laundry is moving, and thus more air bubble layers are formed as the laundry in a close contact with the pulsator 13 moves farther therefrom.

Meanwhile, as a result of determination in operation 212, when the measured time period is greater than the first time period, the controller 52 stops the washing motor 14 through the drive unit 56 (214).

When the washing motor 14 is stopped, counter electromotive force of the washing motor 14 is generated. Due to the generated counter electromotive force, the photo coupler 61 of the load detector 60 performs On/Off operation, and the transistor 62 performs On/Off operation in accordance with the On/Off operation of the photo coupler 61, thereby generating pulse signals.

The high or low pulse signal generated according to the On/Off operation of the transistor 62 is input to the controller 52, and the controller 52 counts the pulse signals (215).

As such, the controller 52 continuously measures the pulse count during the overload detecting cycle in which the washing motor 14 is rotated clockwise and counterclockwise for a predetermined time period.

Then, the controller 52 counts a time period taken to stop the washing motor 14 and determines whether the counted time period is greater than the second time period (about 0.7 seconds) (216).

As a result of determination in operation 216, when the measured time period is less than the second time period, the controller 52 feeds back to operation 214 and performs subsequent operations.

As such, when the washing motor 14 is stopped for the second time period (about 0.7 seconds) after being driven in the reverse direction, more air bubble layers formed around the pulsator 13 flow between laundry items.

Meanwhile, as a result of determination in operation 216, when the measured time period is greater than the second time period, the controller 52 counts a time period T taken to drive the washing motor 14 in the regular direction and the reverse direction (hereinafter, referred to as clockwise/counterclockwise rotation time) (218).

Then, the controller 52 determines whether the counted clockwise/counterclockwise rotation time T reaches a predetermined reference rotation time Ts (e.g., about 30 seconds, capable of detecting overload conditions of the washing motor 14) (220).

As a result of determination in operation 220, when the motor clockwise/counterclockwise rotation time T is less than the reference rotation time Ts, the controller 52 feeds back to operation 202 and continues the overload detecting cycle of strongly rotating the pulsator 13 clockwise and counterclockwise by driving the washing motor 14 in the regular direction and the reverse direction until the clockwise/counterclockwise rotation time T reaches the reference rotation time Ts.

Meanwhile, as a result of determination in operation 220, when the clockwise/counterclockwise rotation time T reaches the reference rotation time Ts, the controller 52 stops the overload detecting cycle.

Meanwhile, according to the illustrated embodiment, the motor RPM of the overload detecting cycle is maintained at 530 RPM. However, the embodiments of the present disclosure are not limited thereto, and the same objects and effects may be achieved when the motor RPM of the overload detecting cycle is maintained at 500 RPM or higher.

In addition, according to the illustrated embodiment, the motor operation factor is constantly maintained regardless of the clockwise/counterclockwise rotation time T when the washing motor 14 is rotated clockwise and counterclockwise at a motor operation factor of 1.0 sec On and 0.7 sec Off for a predetermined time period (about 30 seconds) while maintaining the motor RPM at 530 RPM during the overload detecting cycle as illustrated in FIG. 7. However, the embodiments of the present disclosure are not limited thereto, and the same objects and effects may be achieved even when On or Off time of the motor operation factor is changed in accordance with the clockwise/counterclockwise rotation time T.

Besides, the motor RPM and the operation factor may be changed when the washing motor 14 is overloaded. This will be described with reference to FIGS. 9 and 10.

FIG. 9 is a graph illustrating motor driving profile 2 during an overload detecting cycle of a washing machine 1 according to an embodiment of the present disclosure. When an overload of the washing motor 14 is detected, a motor operation factor is changed from motor driving profile 1 of FIG. 8.

FIG. 9 illustrates an overload detecting cycle in which the motor operation factor is constantly maintained regardless of the clockwise/counterclockwise rotation time T when the washing motor 14 is rotated clockwise and counterclockwise at a motor operation factor of 1.3 sec On and 0.4 sec Off for a predetermined period of time (about 30 seconds) while maintaining the motor RPM at 530 RPM.

FIG. 10 is a graph illustrating motor driving profile 3 during an overload detecting cycle of a washing machine 1 according to an embodiment of the present disclosure. When an overload of the washing motor 14 is detected, the RPM and the motor operation factor are changed from motor driving profile 1 of FIG. 8.

FIG. 10 illustrates an overload detecting cycle in which the motor operation factor is constantly maintained regardless of the clockwise/counterclockwise rotation time T when the washing motor 14 is rotated clockwise and counterclockwise at a motor operation factor of 1.3 sec On and 0.4 sec Off for a predetermined period of time (about 30 seconds) while maintaining the motor RPM at 600 RPM.

Referring to FIGS. 9 and 10, the motor operation factor is constantly maintained regardless of the clockwise/counterclockwise rotation time T when the washing motor 14 is rotated clockwise and counterclockwise at a motor rotation factor of 1.3 sec On and 0.4 sec Off for a predetermined time period (about 30 seconds) while maintaining the motor RPM at 530 RPM or 600 RPM during the overload detecting cycle. However, the embodiments of the present disclosure are not limited thereto, and the same objects and effects may be achieved even when On or Off time of the motor operation factor is changed in accordance with the clockwise/counterclockwise rotation time T.

Although a few embodiments of the present disclosure have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the disclosure, the scope of which is defined in the claims and their equivalents. 

What is claimed is:
 1. A method of controlling a washing machine comprising a washing tub to accommodate laundry, a pulsator rotatably installed in the washing tub, and a motor to rotate the pulsator, the method comprising: setting a level of water supplied to the washing tub; rotating the motor clockwise and counterclockwise after supplying water to the washing tub up to the set water level; detecting an overload of the motor while rotating the motor clockwise and counterclockwise; and changing the set water level to a higher water level when the overload of the motor is detected and performing cycles of the washing machine.
 2. The method according to claim 1, wherein the setting of the water level is performed after detecting weight of the laundry.
 3. The method according to claim 2, wherein the setting of the water level is performed by setting the water level according to the detected weight of the laundry.
 4. The method according to claim 2, wherein the setting of the water level is performed by selecting the water level according to manipulation by a user.
 5. The method according to claim 4, wherein the detecting of the overload of the motor is performed after a water supplying cycle of initially supplying water to wash the laundry.
 6. The method according to claim 1, wherein the detecting of the overload of the motor is performed before performing the cycles of the washing machine.
 7. The method according to claim 1, wherein the rotating of the motor clockwise and counterclockwise comprises: rotating the motor in one direction for a first time period; stopping the rotation of the motor for a second time period after rotating the motor in the one direction; rotating the motor in the opposite direction for a third time period after the second time period; and stopping the rotation of the motor for a fourth time period after rotating the motor in the opposite direction.
 8. The method according to claim 7, further comprising counting pulse signals generated by counter electromotive force of the motor while the motor is stopped.
 9. The method according to claim 8, further comprising: counting a time period taken to rotate the motor clockwise and counterclockwise; and stopping the rotation of the motor clockwise and counterclockwise when the counted time period is greater than a predetermined time period.
 10. The method according to claim 9, wherein the detecting of the overload of the motor is performed by determining that the motor is overloaded when a sum of the counted pulse signals is less than a reference value.
 11. The method according to claim 1, wherein the changing of the set water level is performed by changing the set water level to a highest water level.
 12. The method according to claim 7, wherein the rotating of the motor in one direction is performed by rotating the motor in a regular direction for the first time period while maintaining a constant motor RPM.
 13. The method according to claim 12, wherein the rotating of the motor in the opposite direction is performed by rotating the motor in the reverse direction for the third time period while maintaining a constant motor RPM.
 14. The method according to claim 13, further comprising changing the motor RPM when the motor is rotated clockwise and counterclockwise.
 15. The method according to claim 7, further comprising motor driving time or motor stopping time while rotating the motor clockwise and counterclockwise.
 16. A method of controlling a washing machine comprising a washing tub to accommodate laundry, a pulsator rotatably installed in the washing tub, and a motor to rotate the pulsator and the washing tub, the method comprising: rotating the motor clockwise and counterclockwise after a water supplying cycle to supply water to a set water level for washing the laundry; detecting an overload of the motor while rotating the motor clockwise and counterclockwise; and changing the set water level to a highest water level when the overload of the motor is detected and performing cycles of the washing machine.
 17. A washing machine comprising: a washing tub to accommodate laundry; a pulsator rotatably installed in the washing tub; a motor to rotate the pulsator; a load detector to detect a weight of the laundry; and a controller to perform an overload detecting cycle by rotating the motor clockwise and counterclockwise after supplying water to the washing tub up to a set water level, and detecting an overload of the motor using the load detector while the motor is rotated clockwise and counterclockwise, wherein the overload detecting cycle to detect an overload by performing an operation of rotating the motor clockwise and counterclockwise for a predetermined time period comprises rotating the motor in one direction for a first time period after supplying water to the washing tub; stopping the rotation of the motor for a second time period after rotating the motor in the one direction; rotating the motor in the opposite direction for a third time period after the second time period; and stopping the rotation of the motor for a fourth time period after rotating the motor in the opposite direction.
 18. The washing machine according to claim 17, wherein the controller counts pulse signals generated by counter electromotive force of the motor while the motor is stopped during the rotation of the motor, compares a sum of the counted pulse signals with a reference value, and determines that the motor is overloaded when the counted pulse is less than the reference value.
 19. The washing machine according to claim 18, wherein the controller sets the water level according to the detected weight of the laundry.
 20. The washing machine according to claim 19, wherein the controller changes the set water level to a higher water level when the overload of the motor is detected.
 21. The washing machine according to claim 18, further comprising an input unit to select a level of water supplied to the washing tub, wherein the controller changes the selected water level to a higher water level when an overload of the motor is detected.
 22. The washing machine according to claim 21, wherein the controller changes the set water level to a highest water level. 